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Re: Pg_upgrade speed for many tables

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>,Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>,Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,Magnus Hagander <magnus(at)hagander(dot)net>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Pg_upgrade speed for many tables
Date: 2012-11-05 22:03:45
Message-ID: 20121105220321.GA6125@anarazel.de (view raw or flat)
Thread:
Lists: pgsql-hackers
On Mon, Nov 05, 2012 at 04:42:56PM -0500, Bruce Momjian wrote:
> On Mon, Nov  5, 2012 at 04:39:27PM -0500, Robert Haas wrote:
> > On Mon, Nov 5, 2012 at 4:33 PM, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote:
> > > AFAIR any transaction that modifies catalogs gets sync commit forcibly,
> > > regardless of the setting.  And sync commit means you get to wait for
> > > all previous transactions to be flushed as well.  So simply creating a
> > > temp table ought to do the trick ...

SET synchronous_commit = on;
SELECT txid_current();

Should be enough.

> > I don't think there's a carve-out for system tables ... but creating a
> > temp table with synchronous_commit=on will certainly do the trick.
>
> What is a temp table writing to WAL?  The pg_class/pg_attribute changes?

Yes.

Andres


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